ALSA: oss: avoid missing-prototype warnings

Two functions are defined and used in pcm_oss.c but also optionally
used from io.c, with an optional prototype. If CONFIG_SND_PCM_OSS_PLUGINS
is disabled, this causes a warning as the functions are not static
and have no prototype:

sound/core/oss/pcm_oss.c:1235:19: error: no previous prototype for 'snd_pcm_oss_write3' [-Werror=missing-prototypes]
sound/core/oss/pcm_oss.c:1266:19: error: no previous prototype for 'snd_pcm_oss_read3' [-Werror=missing-prototypes]

Avoid this by making the prototypes unconditional.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20230516195046.550584-2-arnd@kernel.orgSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/oss/pcm_plugin.h

@@ -141,6 +141,14 @@ int snd_pcm_area_copy(const struct snd_pcm_channel_area *src_channel,
 
 void *snd_pcm_plug_buf_alloc(struct snd_pcm_substream *plug, snd_pcm_uframes_t size);
 void snd_pcm_plug_buf_unlock(struct snd_pcm_substream *plug, void *ptr);
+#else
+
+static inline snd_pcm_sframes_t snd_pcm_plug_client_size(struct snd_pcm_substream *handle, snd_pcm_uframes_t drv_size) { return drv_size; }
+static inline snd_pcm_sframes_t snd_pcm_plug_slave_size(struct snd_pcm_substream *handle, snd_pcm_uframes_t clt_size) { return clt_size; }
+static inline int snd_pcm_plug_slave_format(int format, const struct snd_mask *format_mask) { return format; }
+
+#endif
+
 snd_pcm_sframes_t snd_pcm_oss_write3(struct snd_pcm_substream *substream,
 				     const char *ptr, snd_pcm_uframes_t size,
 				     int in_kernel);
@@ -151,14 +159,6 @@ snd_pcm_sframes_t snd_pcm_oss_writev3(struct snd_pcm_substream *substream,
 snd_pcm_sframes_t snd_pcm_oss_readv3(struct snd_pcm_substream *substream,
 				     void **bufs, snd_pcm_uframes_t frames);
 
-#else
-
-static inline snd_pcm_sframes_t snd_pcm_plug_client_size(struct snd_pcm_substream *handle, snd_pcm_uframes_t drv_size) { return drv_size; }
-static inline snd_pcm_sframes_t snd_pcm_plug_slave_size(struct snd_pcm_substream *handle, snd_pcm_uframes_t clt_size) { return clt_size; }
-static inline int snd_pcm_plug_slave_format(int format, const struct snd_mask *format_mask) { return format; }
-
-#endif
-
 #ifdef PLUGIN_DEBUG
 #define pdprintf(fmt, args...) printk(KERN_DEBUG "plugin: " fmt, ##args)
 #else